The present invention relates to a door system, and more particularly to a door system suitable for use of a linear motor.
In a conventional door system, a door is driven by a rotary motor. Such a conventional door system, however, requires a mechanism for converting a rotary motion into a linear motion, a reduction gear and other components including a belt, which complicate the system structure and obstructs its reduction in size. For instance, there are disclosed door systems in JP-A-10-139325 and JP-A-8-275493, in each of which a linear motor is used in place of a rotary motor to drive the door. The linear motor may be either an induction motor or a magnet motor. The door systems, in which a linear motor incorporated in each door hanger generates a thrust in the opening/closing direction to directly drive the door, have no mechanism for converting a rotary motion into a linear motion nor reduction gears, which are found in any door system using a rotary motor. Thus, The door systems have reliable and compact configurations with few expendable components and parts needing lubrication.
However, the linear motors used in the already proposed door systems have some problems. The induction motor, whose structure essentially involves a wide magnetic air gap between the primary and secondary sides, has a problem that its output power is smaller than the input. The linear magnet motor, which comprises generally U-shaped cores to be electromagnets and permanent magnets, takes a long time and a much cost when manufacturing, because a coil must be wound around each core. Or a motor having permanent magnets opposed to magnetic pole faces with an air gap therebetween, also has a problem of a low output power relative to the input because of a large overall leak from a magnetic flux passing through gaps among magnetic pole teeth of magnetic pole plates.
An object of the invention is to provide a door system which has a simple structure, is easy to manufacture and can obtain a high output power relative to the input.
According to one feature of the invention, a door system comprises a door hanger from which a door is movably suspended, an electric motor for generating a thrust to open and close the door, and a linear motor associating with a link mechanism made of a non-magnetic material for transmitting the thrust generated by the motor to the door. The linear motor comprises an armature to serve as a mover runner and a stator having magnetism, in which it is preferable for the armature to have at least a magnetic pole of a first polarity having a first opposed part and another magnetic pole of a second polarity having a second opposed part, and the stator is held in the second opposed part. It is further preferable for the linear motor, comprising the armature as a mover runner and the stator having magnetism, to be so constituted that relative positions of the mover runner in its moving direction and the vertical direction be held by mutual actions of the armature and the stator.